(a). Field of the Invention
The present invention relates to a data recording medium and a data recording/reproducing device and, more particularly, to a technique for positioning control of recording/reproducing heads onto a desired track of a recording medium by using a servo-burst signal.
In a computer system, hard disk drives are widely used for storing a large amount of information. For increasing the recording capacity of the hard disk drive, it is desired to increase the recording density of the recording disk in the circumferential direction (moving direction) as well as the radial direction (direction normal to the moving direction) of the recording disk. The increase of the recording density in the radial direction can be achieved by increasing the track density of the recording disk.
The increase of the tracking density highlights an error due to vibration or thermal expansion in the relative location of the recording/reproducing head with respect to the recording disk in the radial direction. The correction of the position error is generally achieved by using a servo-burst pattern recorded on the recording disk. Specifically, the reproducing head reads the servo-burst pattern, which is then subjected to signal processing by a tracking system of the disk drive for accurately positioning the reproducing head onto the data track.
FIG. 1 shows a part of a conventional recording disk, generally designated by numeral 100, using a sampled servo-burst scheme. In the recording disk 100, each data track 11 is periodically divided into a plurality of data blocks 12 in a circumferential direction (U), and a plurality of data blocks 12 arranged in the radial direction (R) from the inner periphery to the outer periphery of the disk forms a data area 10. A servo-burst area 20 is provided between each adjacent two of the data area 10. In the servo-burst area 20, four types of servo-burst signals A, A.sup.-, B and B.sup.- are successively recorded in the circumferential direction, wherein each type of servo-burst signals is disposed in a column extending in the radial direction. Signal "A" and signal "B" have an equal length, which is equal to the track pitch "p", and deviated in the radial direction by p/2 from each other. Signal A.sup.- and signal B.sup.- are recorded at the locations where signal A and signal B, respectively, are not recorded, i.e., at the locations where A.sup.- and B.sup.- supplement signal A and signal B, respectively. The centers of signals A and A.sup.- as viewed in the radial direction are aligned with the centers of the gaps between the adjacent data tracks 11, whereas the centers of signals B and B.sup.- as viewed in the radial direction are aligned with the centers of the data tracks 11.
The recording/reproducing device includes a single reproducing head (or a single recording and reproducing head) 31, which reproduces the servo-burst signals. The reproduced signal provides the amount of displacement of the head with respect to the center of the data track 11 for allowing the recording/reproducing device to control the location of the reproducing head.
In the conventional recording disk 100 having the servo-burst area as described above, the servo-burst signals arranged in the four columns occupy a large area, which reduces the data areas or effective user area in the recording disk.
In addition, with the recent increase of the track density of the recording disk, about 2 kHz is generally required for the response frequency of the servo-burst signal, whereas as high as about 20 kHz is required for the frequency of the servo-burst signal itself. In the disk drive adapted for the high frequency and having a rotational speed higher than 100 rps (rotations per second) or 6000 rpm (rotations per minute), the number of servo-burst signals required in a single rotation ranges 100 to 200. This involves a problem of reduced recording capacity due to the large occupied area for the servo-burst signals and a reduced user area.